How to create keyframes for Animation Nodes, which I can see in dope sheet?
Unfortunally it is currently a limitation in Blender that keyframes you set on properties of a custom node are not visible in the Dope Sheet.

I suggest you create a controller object in the 3d view that you can animate normally. Than you can use eg the x location of that object to control the procedual animation. 

A benefit of this method is that you don't have to have the node editor open to change the value. You can simply move your controller object and see your animation adapting to that.

To get the x location of that object you need the Object Transforms Input and a Separate Vector node.